Grid support wedges



.between the electrode support rods.

GRID SUPPORT WEDGES Wenfoo George Woo, West Newton, Mass., assignor toRaytheon Company, a corporation of Delaware Application June 13, 1955,Serial No. 514,820

8 Claims. (Cl. 313 -260) This invention relates to electron dischargedevices and their construction, and more particularly to wedges forretaining grid supports in place in separators.

In electron discharge devices any change in the relative positions ofthe electrodes, particularly of the grids, will cause variations in theelectrical output of the tube. This appears as noise in the output of anoperating tube. A common cause of such changes in the relative positionsof the electrodes is the play of the support rods within the holes inwhich they are mounted in separators, usually of mica. This can beprevented by tightening the tolerances to which the holes for thesupport rods are drilled in the mica. However, if this is done, thealready difiicult task of inserting the support rods of theelectrodesinto the holes in the spacer is made even more ditficult with the resultthat production is slowed down and made more 1 expensive. In fact, themore play that can be tolerated, the easier is the assembly operation.Another diiiiculty with making the holes in the spacers for the supportrods to close tolerances, is that the holes are enlarged in the processof pushing the rods through them. Furthermore, 1

when the cathode sleeve heats during processing and operation, it willdistort the openings. Stakes have been used to give added rigidity tothe electrode supports, but this construction is expensive and in thesubrniniature size of tube there is no room to spare on the separatorfor stakes. Another approach has been to insert small metal springs Thisagain is an expensive construction. In addition, the metal of thesprings is likely to lose its temper when the mount is heated, eitherduring processing or during the operation of the tube and cease toperform its function of forcing the electrode supports toward the sidesof the holes in the separators, thus permitting the play to take placeand create noise. A possibility is to melt glass about the electrodesupports as they protrude from the spacer. While this is effective instopping play, it is expensive.

By the construction of the invention, a piece of mica,

or other insulating material is formed with a region of a dimensiondetermined by the desired spacing of the electrode supports and formedby two opposing notches of a depth and width determined by the radius ofthe support rods to be separated. The notches are preferably trapezoidalin shape, although they may be of other shapes, such as triangular orsemicircular. The wedge is inserted edgewise between the electrodesupports and turned fiat as it approaches the spacer. It is held downand in position by a second spacer inserted about the electrode supportsover the wedges. The result is that the electrodes are retained in theirrelative spacing even when the holes in the mica are formed to greaterthan their normal tolerances. These larger tolerances speed up assemblyof the mounts making the construction cheaper. Tubes constructed withthe wedges of the invention produced no vibration output that could betraced to motion of the grid or gn'ds. In a representative case,microphonic output was reduced from 300 millivolts to millivolts.

2,910,608 l atented Oct. 27, 1959 ice The foregoing and other advantagesof this invention will be better understood from the followingdescription taken in conjunction with the accompanying drawing wherein:

Fig. l is an exploded isometric view of a tube mount assembled with thewedges of the invention; v

Fig. 2 is a view takenalong the line 2-2 of- Fig. 3 of a mount with thewedges of the invention inserted within an envelope (only a part shown);

Fig. 3 is a View taken along the line 3'-3 of Fig. 2 partially brokenaway of a tube with the wedges of the invention; and

Figs. 4a, 4b and 4c are plan views of three forms of the wedges of theinvention.

In Fig. 1 the reference numeral 10 designates the lower of two upperspacers of insulating material, preferably mica, formed with openingsthrough which are inserted the electrode supports 11, 12, 13, 14, 15 and16, the cathode sleeve 17 and two tabs 18 and 20 formed integral withthe anode 21. The support rods 13 and 14 support the first grid 22, bestseen in Fig. 3. The supports 12 and 15 support the screen grid 22a, andsupports 11 and 16 support the suppressor grid 22b, also best seen inFig. 3. Two wedges 23 are formed of insulating material, preferably ofmica, each with a notch 24 in each side, leaving a restricted region 25.These wedges may be of. any of the shapes shown in Figs. 4a, 4b and 4c.Fig. 4a shows the preferred configuration. in which the notch is oftrapezoidal shape. The depth a, an outer b, and

an inner c widths of this notch are determined by the radius of theassociated rods at the region of contact. The width of the restrictedregion 25 is determined by the desired spacing between the associated.rods. Mica is suificiently soft so that if the dimension d ismades'lightly larger than the desired spacing, the rod will fracture offenough mica to complete the cutting of the notch and give a tight fitwithout buckling or weakening the mica. The notches of the trapezoidalshape, shown in Fig. 4a, are easier to form in the mica than thesemicircular notches 24a of radius r, considerably greater than theradius of the associated rods shown in Fig. 4b. However, a semicircularnotch accommodates a rod of circular cross section better than thetriangular notches 24b, shown in Fig. 40. This particular type of notchis the easiest to make, but it is necessary to make the dimension dconsiderably smaller for the same spacing of the associated grid supportro'ds, than for either of the other two shapes. This weakens the wedge.Thus the form of the wedge shown in Fig. 4a has been found to be best,but other constructions for achieving the region of 7 reduced width,such as those shown in Figs. 4b and 40, can be used.

When the wedges are inserted, they are held in place by a second spacer26 formed with an opening 27 to receive the support rods 11 through 16,and with an enlargement 27a at .the center to receive the cathode sleeve17. It is also formed with slots 28 and 30 to receive the tabs 18 and 20that support the anode 21. Individual openings might be formed in thespacer 26 for each electrode support, but all that is needed is a meansfor holding down both those portions of each wedge that protrude beyondthe space between the electrode supports. Separate openings wouldrequire each electrode support to be inserted in its opening, slowingassembly and increasing cost. The result of the construction of theinvention is the sandwich shown in Fig. 3' where the spacer 10 forms thebottom layer with the electrode supports 11 through 16, the cathodesleeve 17, and the tabs 18 and 20 passing through it. The wedges 23,shown in cross section as the middle layer, are inserted between theirassociated support rods 12 and 13, and 14 and 15, respectively. It willbe seen that when the mount is inserted in the envelope 31 theprotrusions 32, formed on the spacers and 26, serve to support the mounttransversely in the envelope without conducting excessive heat to theregionof contact. Other spacer configurations can of course be used.Wedges of the invention may be used between the lower ends of theelectrode supports as well.

This invention is not limited to the particular details of construction,materials and processes described, as many equivalents will suggestthemselves to those skilled in the art. It is accordinglydesired thatthe appended claims be given a broad interpretation commensurate withthe scope of the invention within the art.

What is claimed is:

1. An electron discharge device including a plurality of electrodes withsupport members inserted in openings in spacer members, wedge membersplaced between at least two adjacent electrode support members wherethey protrude from at least one of the spacer members, said wedgemembers comprising a flat strip of insulating material of a hardnessless than that of the support members having a region of reduced width,said width being slightly greater than that required by the desiredseparation of the adjacent electrode supports, said region of reducedwidth being formed by opposing notches of a width and .depth determinedby the cross-sectional dimensions of the adjacent electrode supports atthe region of contact, the width of said notches reducing with depth.

2. An electron discharge device includinga plurality of electrodes withsupport members inserted in openings in spacer members,.wedge membersplaced between at least two adjacent electrode support members wherethey protrude from at leastone of the spacer members, said wedge memberscomprising a flat strip of insulating material of a hardness less thanthat of the support members having a region of reduced width, said widthbeing slightly greater than that required by the desired separation ofthe adjacent electrode supports, said region of reduced width beingformed by opposing semicircular notches of a radius determined by thecross-sectional dimensions of the adjacent electrode supports at theregion of contact.

7 3. An electron discharge device including a plurality of electrodeswith support members inserted in openings in spacer members, wedgemembers placed between at least two adjacent electrode support memberswhere they protrude from at least one of the spacer members, said wedgemembers comprising a-flat strip of insulating material of a hardnessless than that of the support members having a region of reduced width,said width being slightly greater than that required by the desiredseparation of. the adjacent electrode supports, said region of reducedwidth being formed by opposing notches of a triangular shape with awidth and depth determined by the cross-sectional dimensions of theadjacent electrode Y supports at the region of contact.

wedge membe 5. comprising a fiat strip of insulating material of ahardness less than that of the support members having a region ofreduced width, said width being slightly greater than that required bythe desired separation of the adjacent electrode supports, said regionof reduced width being formed by opposing notches of a trapezoidal shapewith dimensions determined by the cross-sectional dimensions of theadjacent electrode supports at the region of contact, the width of saidnotches reducing with depth.

5. Wedge members for separating the electrode supports of electrondischarge devices formed of a flat strip of insulating material of ahardness less than that of said supports with a region of reduced width,said width being slightly greater than that required by the desiredseparation of the electrode supports to be separated, said region ofreduced width being formed by opposing notches of a width and depthdetermined by the cross-sectional dimensions of the electrode supportswith which the wedge is to be adjacent at the region of contact, thewidth of said notches reducing with depth.

6. Wedge members for separating the electrode supports of electrondischarge devices formed of a fiat strip of insulating material of ahardness less than that of said supports with a region of reduced width,said width being slightly greater than that required by the desiredseparation of the electrode supports to be separated, said region ofreduced width being formed by opposing semicircular notches ot a radiusdetermined by the crosssecti-onal dimensions or" the electrode supportswith which the Wedge is to be associated at the region of contact.

7. Wedge members for separating the electrode supports of electrondischarge devices formed of a flat strip of insulating material of ahardness less than that of said supports with a region of reduced width,staid width being slightly greater than that required by the desiredseparation of the electrode supports to be separated, said region ofreduced width being formed by opposing notches of a triangular shapewith a width and depth determined by the cross-sectional dimensions ofthe electrode supports with which the wedge is to be associated at theregion of contact.

8. Wedge members for separating the electrode sup ports of electrondischarge devices formed of a'fiat strip of insulating material of ahardness less than that of said supports with a region of reduced width,said Width be ing slightly greater than that required by the desiredseparation of the electrode supports to be separated, said region ofreduced width being formed by opposing notches of a trapezoidal shapewith dimensions determined by the cross-sectional dimensions of theelectrode supports with which the wedge is to be associated at theregion of contact, the width of said notches reducing with depth.

References Cited in the file of this patent UNITED STATES PATENTS289,166 Strohm Nov. 27, 1883 1,801,451 Parker Apr. 21, 1931 1,867,390Thompson July 12, 1932 1,886,991 Van Horne Nov. 8, 1 932 2,057,115 RotheOct. 13, 1936

